Optical calculators

Quick, accurate calculators that show their working — so you learn the method, not just the answer.

Prentice's Rule calculator

Induced prism and base direction from lens power and decentration — horizontal, vertical, and resultant.

Convert between plus- and minus-cylinder form, with the power cross and spherical equivalent.

Calculators are study aids. Always verify finished eyewear with your instruments and follow your practice's procedures.